Azo dyes containing 2-amino-3-cyano-5-formylthiophene derivatives as diazo components and substituted aniline compounds as coupling components

ABSTRACT

The compounds of the formula I ##STR1## where R is unsubstituted or substituted phenyl or naphthyl, R 1  and R 2  are each unsubstituted or substituted alkyl, alkenyl or cycloalkyl, and one of the radicals may furthermore be hydrogen, R 3  is hydrogen, methyl, methoxy, ethoxy or chlorine, and R 4  is acylamino, are particularly useful for dyeing polyesters.

The present invention relates to compounds of general formula I ##STR2## where R is unsubstituted or substituted phenyl or naphthyl, R¹ and R² are each unsubstituted or substituted alkyl, alkenyl or cycloalkyl, and one of the radicals may furthermore be hydrogen, R³ is hydrogen, methyl, methoxy, ethoxy or chlorine and R⁴ is acylamino.

The radicals R may be substituted by, for example, fluorine, chlorine, bromine, trifluoromethyl, C₁ -C₄ -alkyl or -alkoxy, nitro or cyano, chlorine, methyl and methoxy being preferred.

R¹ and R² are each, for example, C₁ -C₆ -alkyl which may furthermore be substituted by hydroxyl, C₁ -C₄ -alkoxy, phenoxy, phenyl, cyano, alkanoyl, alkanoyloxy, alkoxycarbonyl, aroyloxy, alkoxycarbonyloxy, alkylaminocarbonyloxy, arylaminocarbonyloxy or alkoxy-alkoxy, or are each C₂ -C₄ -alkenyl or C₅ -C₇ -cycloalkyl.

Specific examples of radicals R¹ and R² are methyl, ethyl, propyl, butyl, pentyl, hexyl, allyl, methallyl, 2-chloroethyl, 2-bromoethyl, 2-cyanoethyl, 2-hydroxyethyl, 2-phenyl-2-hydroxyethyl, 2,3-dihydroxypropyl, 2-hydroxypropyl, 2-hydroxybutyl, 2-hydroxy-3-phenoxypropyl, 2-hydroxy-3-methoxypropyl, 2-hydroxy-3-butoxypropyl, 3-hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-butoxyethyl, 2-phenoxyethyl, 2-phenoxypropyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 2-isobutyryloxyethyl, 2-methoxymethylcarbonyloxyethyl, 2-ethoxymethylcarbonyloxyethyl, 2-phenoxymethylcarbonyloxyethyl, 2-methoxycarbonyloxyethyl, 2-ethoxycarbonyloxyethyl, 2-propoxycarbonyloxyethyl, 2-butoxycarbonyloxyethyl, 2-phenyloxycarbonyloxyethyl, 2-benzyloxycarbonyloxyethyl, 2-methoxyethoxycarbonyloxyethyl, 2-ethoxyethoxycarbonyloxyethyl, 2-propoxyethoxycarbonyloxyethyl, 2-butoxyethoxycarbonyloxyethyl, 2-methylaminocarbonyloxyethyl, 2-ethylaminocarbonyloxyethyl, 2-propylaminocarbonyloxyethyl, 2-butylaminocarbonyloxyethyl, 2-methoxycarbonylethyl, 2-ethoxycarbonylethyl, 2-propoxycarbonylethyl, 2-butoxycarbonylethyl, 2-phenoxycarbonylethyl, 2-benzyloxycarbonylethyl, 2-β-phenylethoxycarbonylethyl, 2-methoxyethoxycarbonylethyl, 2-ethoxyethoxycarbonylethyl, 2-propoxyethoxycarbonylethyl, 2-butoxyethoxycarbonylethyl, 2-phenoxyethoxycarbonylethyl and 2-benzoylethyl, and one of the radicals may furthermore be hydrogen.

Examples of suitable radicals R⁴ are unsubstituted or substituted C₁ -C₆ -alkanoylamino, unsubstituted or substituted benzoylamino and C₁ -C₄ -alkylsulfonylamino or -dialkylaminosulfonylamino.

Specific examples of radicals R⁴ are methylcarbonylamino, ethylcarbonylamino, n- and isopropylcarbonylamino, n-, iso- and sec-butylcarbonylamino, benzylcarbonylamino, benzoylamino, o-, m- and p-methylbenzoylamino, o-, m- and p-chlorobenzoylamino, o-, m- and p-methoxybenzoylamino, o-, m- and p-nitrobenzoylamino, methylsulfonylamino, ethylsulfonylamino, propylsulfonylamino, methoxymethylcarbonylamino and ethoxy-, phenoxy-, cyano-, chloro- and bromomethylcarbonylamino.

The compounds of the formula I can be prepared by reacting a diazonium salt of a compound of the formula I ##STR3## with a coupling component of the formula ##STR4## by a conventional method. The Examples which follow illustrate the preparation. Parts and percentages are by weight, unless stated otherwise.

The compounds of the formula I are preferably used for dyeing synthetic polyesters; essentially blue hues are obtained, some of them possessing very good fastness properties.

Of particular importance are compounds of the formula I in which R is phenyl which is unsubstituted or substituted by chlorine, bromine, methyl, ethyl, methoxy or ethoxy, R¹ and R² are each allyl, benzyl, phenylethyl or C₁ -C₄ -alkyl which is unsubstituted or substituted by hydroxyl, cyano, C₁ -C₄ -alkanoyloxy, C₁ -C₄ -alkoxycarbonyl or C₁ -C₄ -alkoxy, and one of the radicals may furthermore be hydrogen, R³ is hydrogen, methyl, methoxy or ethoxy and R⁴ is C₁ -C₄ -alkanoylamino, methoxy-, ethoxy-, phenoxy-, cyano- or chloromethylcarbonylamino, C₁ -C₄ -alkylsulfonylamino or benzoylamino.

EXAMPLE 1

22.8 parts of 2-amino-3-cyano-4-phenyl-5-formylthiophene were introduced into a mixture of 150 parts by volume of glacial acetic acid/propionic acid (3:1) and 50 parts by volume of 85% strength sulfuric acid. 17.5 parts by volume of nitrosylsulfuric acid (11.5% of N₂ O₃) were added dropwise at 0°-5° C., after which the mixture was stirred for 4 hours at this temperature.

24.6 parts of 3-diethylaminoacetanilide were dissolved in 100 parts by volume of dimethylformamide, and the solution was added to 250 parts of water, 50 parts by volume of 32% strength hydrochloric acid, 1000 parts of ice and 2.5 parts of amidosulfonic acid. The diazo solution obtained beforehand was added in the course of 0.5 hour, with external cooling with ice/water, and the mixture was stirred for 4 hours at 0°-5° C. and overnight without further cooling. The product was filtered off under suction, washed neutral with water and dried at 60° C. in a drying oven under reduced pressure to give 38 parts of a blueish black powder of the formula ##STR5## which dyes polyesters in fast blue hues.

The dyes defined in the Table below were obtained by a similar method.

    __________________________________________________________________________      ##STR6##                                                                      Example No.                                                                           R          R.sup.1   R.sup.2    R.sup.3                                                                             R.sup.4   Color on                 __________________________________________________________________________                                                           PES                       2     C.sub.6 H.sub.5                                                                           CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       H    NHCOCH.sub.3                                                                             blue                      3     C.sub.6 H.sub.5                                                                           CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       H    NHCOC.sub.6 H.sub.5                                                                      blue                      4     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOC.sub.6 H.sub.5                                                                      blue                      5     C.sub.6 H.sub.5                                                                           C.sub.4 H.sub.9 (n)                                                                      C.sub.4 H.sub.9 (n)                                                                       H    NHCOCH.sub.3                                                                             blue                      6     C.sub.6 H.sub.5                                                                           C.sub.6 H.sub.13 (n)                                                                     C.sub.6 H.sub.13 (n)                                                                      H    NHCOCH.sub.3                                                                             blue                      7     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               H    NHCOCH.sub.3                                                                             blueish violet            8     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               H    NHCOC.sub.6 H.sub.5                                                                      blueish violet            9     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 CN                                                                       CH.sub.2 CHCH.sub.2                                                                       H    NHCOC.sub.6 H.sub.5                                                                      blueish violet           10     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 CN                                                                       C.sub.4 H.sub.9 (n)                                                                       H    NHCOC.sub.6 H.sub.5                                                                      blue                     11     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 CN                                                                        ##STR7##  H    NHCOC.sub.6 H.sub.5                                                                      blueish violet           12     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OCH.sub.3                                                                C.sub.2 H.sub.4 CN                                                                        H    NHCOCH.sub.3                                                                             blue                     13     C.sub.6 H.sub.5                                                                           CH.sub.2 CO.sub.2 CH.sub.3                                                               CH.sub.2 CO.sub.2 CH.sub.3                                                                CH.sub.3                                                                            NHSO.sub.2 CH.sub.3                                                                      blueish violet           14     C.sub.6 H.sub.5                                                                           H         C.sub.2 H.sub.4 CO.sub.2 C.sub.2 H.sub.4                                       OC.sub.6 H.sub.5                                                                          H    NHCOCH.sub.3                                                                             blueish violet           15     C.sub.6 H.sub.5                                                                           H         C.sub.2 H.sub.4 OC.sub.2 H.sub.5                                                          Cl   NHCOCH.sub.3                                                                             blue                     16     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub. 4 CN                                                                      CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            17     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 CO.sub.2 CH.sub.3                                                         H    NHCOCH.sub.3                                                                             violet                   18     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OH                                                                       C.sub.2 H.sub.4 CO.sub.2 CH.sub.3                                                         H    NHCOCH.sub.3                                                                             blue                     19     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OH                                                                       CH.sub.2 C.sub.6 H.sub.5                                                                  H    NHCOCH.sub.3                                                                             blue                     20     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OCOCH.sub.3                                                              CH.sub.2 C.sub.6 H.sub.5                                                                  H    NHCOCH.sub.3                                                                             blue                     21     C.sub.6 H.sub.5                                                                           CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            22     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            23     C.sub.6 H.sub.5                                                                           H         C.sub.2 H.sub.4 CO.sub.2 C.sub.4 H.sub.9                                                  OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            24     C.sub.6 H.sub.5                                                                           H         C.sub.2 H.sub.4 CO.sub.2 C.sub.2 H.sub.4                                       OC.sub.4 H.sub.9                                                                          H    NHCOCH.sub.3                                                                             reddish blue             25     p-CH.sub.3 OC.sub.6 H.sub.4                                                               C.sub. 2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.3                                                                             blue                     26     p-CH.sub.3 OC.sub.6 H.sub.4                                                               CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       H    NHCOCH.sub.3                                                                             blue                     27     p-CH.sub.3 OC.sub.6 H.sub.4                                                               C.sub.4 H.sub.9 (n)                                                                      C.sub.4 H.sub.9 (n)                                                                       H    NHCOCH.sub.3                                                                             blue                     28     p-CH.sub.3 OC.sub.6 H.sub.4                                                               C.sub.6 H.sub.13 (n)                                                                     C.sub.6 H.sub.13 (n)                                                                      H    NHCOCH.sub.3                                                                             blue                     29     p-CH.sub.3 OC.sub.6 H.sub.4                                                               CH.sub.2 CHCHCl                                                                          CH.sub.2 CHCHCl                                                                           H    NHCOCH.sub.3                                                                             reddish blue             30     p-CH.sub.3 OC.sub.6 H.sub.4                                                               C.sub.2 H.sub.4 CN                                                                       C.sub.4 H.sub.9 (n)                                                                       H    NHCOC.sub.6 H.sub.5                                                                      blue                     31     p-CH.sub.3 OC.sub.6 H.sub.4                                                               C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               H    NHCOC.sub.6 H.sub.5                                                                      reddish blue             32     p-CH.sub.3 OC.sub.6 H.sub.4                                                               C.sub.2 H.sub.4 CN                                                                       CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            33     p-CH.sub.3 OC.sub.6 H.sub.4                                                               CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            34     p-ClC.sub. 6 H.sub.4                                                                      C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.3                                                                             blue                     35     p-ClC.sub.6 H.sub.4                                                                       CH.sub.2 CHCHCl                                                                          CH.sub.2 CHCHCl                                                                           H    NHCOCH.sub.3                                                                             reddish blue             36     p-ClC.sub.6 H.sub.4                                                                       C.sub.6 H.sub.13 (n)                                                                     C.sub.6 H.sub.13 (n)                                                                      H    NHCOCH.sub.3                                                                             blue                     37     p-ClC.sub.6 H.sub.4                                                                       C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               H    NHCOCH.sub.3                                                                             blueish violet           38     p-ClC.sub.6 H.sub.4                                                                       C.sub.2 H.sub.4 CN                                                                        ##STR8##  H    NHCOC.sub.6 H.sub.5                                                                      blueish violet           39     p-ClC.sub.6 H.sub.4                                                                       C.sub.2 H.sub.4 CN                                                                       CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            40     p-ClC.sub.6 H.sub.4                                                                       CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            41     p-CH.sub.3C.sub.6 H.sub.4                                                                 C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.3                                                                             blue                     42     p-CH.sub.3C.sub.6 H.sub.4                                                                 CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       H    NHCOCH.sub.3                                                                             blue                     43     p-CH.sub.3C.sub.6 H.sub.4                                                                 C.sub. 4 H.sub.9 (n)                                                                     C.sub.4 H.sub.9 (n)                                                                       H    NHCOCH.sub.3                                                                             blue                     44     p-CH.sub.3C.sub.6 H.sub.4                                                                 C.sub.6 H.sub.13 (n)                                                                     C.sub.6 H.sub.13 (n)                                                                      H    NHCOCH.sub.3                                                                             blue                     45     p-CH.sub.3C.sub.6 H.sub.4                                                                 CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       H    NHCOC.sub.2 H.sub.5                                                                      blue                     46     p-CH.sub.3C.sub.6 H.sub.4                                                                 C.sub.2 H.sub.4 CN                                                                       CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            47     p-CH.sub.3C.sub.6 H.sub.4                                                                 C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               OCH.sub.3                                                                           NHCOCH.sub.3                                                                             greenish blue            48     o,p-(CH.sub.3).sub.2C.sub.6 H.sub.3                                                       C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.3                                                                             blue                     49     o,p-(CH.sub.3).sub.2C.sub.6 H.sub.3                                                       C.sub.4 H.sub.9 (n)                                                                      C.sub.4 H.sub.9 (n)                                                                       H    NHCOCH.sub.3                                                                             blue                     50     o,p-(CH.sub.3).sub.2C.sub.6 H.sub.3                                                       CH.sub.2 CHCH.sub.2                                                                      CH.sub.2 CHCH.sub.2                                                                       H    NHCOCH.sub.3                                                                             blue                     51     o,p-(CH.sub.3).sub.2C.sub.6 H.sub.3                                                       C.sub.6 H.sub.13 (n)                                                                     C.sub.6 H.sub.13 (n)                                                                      H    NHCOCH.sub.3                                                                             blue                     52     o,p-(CH.sub.3).sub.2 C.sub.6 H.sub.3                                                      C.sub.2 H.sub.4 OCOCH.sub.3                                                              C.sub.2 H.sub.4 OCOCH.sub.3                                                               H    NHCOC.sub.6 H.sub.5                                                                      blue                     53     o,p-(CH.sub.3).sub.2C.sub.6 H.sub.3                                                       C.sub.2 H.sub.4 CN                                                                       CH.sub.2 CHCH.sub.2                                                                       OCH.sub.3                                                                           NHCOCH.sub.3                                                                             blue                     54                                                                                     ##STR9##  C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.3                                                                             blue                     55                                                                                     ##STR10## C.sub.4 H.sub.9 (n)                                                                      C.sub.4 H.sub.9 (n)                                                                       H    NHCOCH.sub.3                                                                             blue                     56                                                                                     ##STR11## C.sub.6 H.sub.13 (n)                                                                     C.sub.6 H.sub.13 (n)                                                                      H    NHCOCH.sub.3                                                                             blue                     57     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.2 OCH.sub.3                                                                   blue                     58     C.sub.6 H.sub.5                                                                           C.sub.3 H.sub.7 (n)                                                                      C.sub.3 H.sub.7 (n)                                                                       H    NHCOCH.sub.2 OCH.sub.3                                                                   blue                     59     C.sub.6 H.sub.5                                                                           C.sub.4 H.sub.9 (n)                                                                      C.sub.4 H.sub.9 (n)                                                                       H    NHCOCH.sub.2 OCH.sub.3                                                                   blue                     60     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.2 OC.sub.2                                                                    blueb.5                  61     C.sub.6 H.sub. 5                                                                          C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.2 Cl                                                                          blue                     62     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.2 CN                                                                          blue                     63     C.sub.6 H.sub.5                                                                           C.sub.2 H.sub.5                                                                          C.sub.2 H.sub.5                                                                           H    NHCOCH.sub.2 OC.sub.6                                                                    blueb.5                  __________________________________________________________________________ 

We claim:
 1. A compound of the formula ##STR12## where R is phenyl or naphthyl; R¹ and R² are each selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, allyl, methallyl, 2-chloroethyl, 2-bromoethyl, 2-cyanoethyl, 2-hydroxyethyl, 2-phenyl-2-hydroxyethyl, 2,3,-dihydroxypropyl, 2-hydroxypropyl, 2-hydroxybutyl, 2-hydroxy-3-phenoxypropyl, 2-hydroxy-3-methoxypropyl, 2-hydroxy-3-butoxypropyl, 3-hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-butoxyethyl, 2-phenoxyethyl, 2-phenoxypropyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 2-isobutyryloxyethyl, 2-methoxymethylcarbonyloxyethyl, 2-ethoxymethylcarbonyloxyethyl, 2-phenoxymethylcarbonyloxyethyl, 2-methoxycarbonyloxyethyl, 2-ethoxycarbonyloxyethyl, 2-propoxycarbonyloxyethyl, 2-butoxycarbonyloxyethyl, 2-phenyloxycarbonyloxyethyl, 2-benzyloxycarbonyloxyethyl, 2-methoxyethoxycarbonyloxyethyl, 2-ethoxyethoxycarbonyloxyethyl, 2-propoxyethoxycarbonyloxyethyl, 2-butoxyethoxycarbonyloxyethyl, 2-methylaminocarbonyloxyethyl, 2-ethylaminocarbonyloxyethyl, 2-propylaminocarbonyloxyethyl, 2-butylaminocarbonyloxyethyl, 2-methoxycarbonylethyl, 2-ethoxycarbonylethyl, 2-propoxycarbonylethyl, 2-butoxycarbonylethyl, 2-phenoxycarbonylethyl, 2-benzyloxycarbonylethyl, 2-β-phenylethoxycarbonylethyl, 2-methoxyethoxycarbonylethyl, 2-ethoxyethoxycarbonylethyl, 2-propoxyethoxycarbonylethyl, 2-butoxyethoxycarbonylethyl, 2-phenoxyethoxycarbonylethyl and 2-benzoylethyl, and one of R¹ and R² may be hydrogen,R³ is hydrogen, methyl, methoxy, ethoxy or chlorine and R⁴ is selected from the group consisting of methylcarbonylamino, ethylcarbonylamino, n- and iso-propylcarbonylamino, n-, iso- and sec-butylcarbonylamino, benzylcarbonylamino, benzoylamino, o-, m- and p-methylbenzoylamino, o-, m- and p-chlorobenzoylamino, o-, m- and p-methoxybenzoylamino, o-, m- and p-nitrobenzoylamino, methylsulfonylamino, ethylsulfonylamino, propylsulfonylamino, methoxymethylcarbonylamino and ethoxy-, phenoxy-, cyano-, chloro- and bromomethylcarbonylamino.
 2. A compound as claimed in claim 1, wherein R is phenyl, R¹ and R² are each allyl, benzyl, phenylethyl or C₁ -C₄ -alkyl which is unsubstituted or substituted by hydroxyl, cyano, C₁ -C₄ -alkanoyloxy, C₁ -C₄ -alkoxycarbonyl or C₁ -C₄ -alkoxy, and one of said radicals may be hydrogen, R³ is hydrogen, methyl, methoxy or ethoxy and R⁴ is C₁ -C₄ -alkanoylamino, methoxy-, ethoxy-, phenoxy-, cyano- or chloromethylcarbonylamino, C₁ -C₄ -alkylsulfonylamino or benzoylamino. 